When a concrete multiple-story (or multiple-floor) building such as a high-rise building and a reactor building is constructed, the building is constructed by casting concrete sequentially from a lowest floor. For example, casting of concrete in a second floor portion is started after casting working of concrete in a first floor portion has been completed by constructing a slab in a ceiling portion of the first floor (a floor portion of the second floor).
It is not preferable that rain water or the like flows into a lower floor that has already been constructed during construction or another work of a floor above the lower floor that has already been constructed. Particularly, to improve construction efficiency, interior finish work or installation of a reactor or equipment may be started in the floor that has already been constructed. In such case, it is strictly essential to prevent the rain water from flowing into the floor.
Generally, one of floors that have already been constructed is employed as a water stop floor to prevent rain water from flowing into downstairs' floors of the water stop floor. The rain water stored on a floor slab of the water stop floor is drained by a pump or the like.
FIG. 6 is a schematic configuration diagram illustrating a conventional drainage system.
As shown in FIG. 6, a conventional temporary drainage system 70 is provided in a reinforced concrete or steel-reinforced concrete multiple-story building 1 under construction. In the multiple-story building 1, a first floor 72 and a second floor 73 have been constructed, and a third floor 74 is being constructed. For example, the second floor 73 is employed as the water stop floor. Rain water flowing from the third floor 74 and floors above the third floor 74 is stopped on a floor slab 75 of the second floor 73 (a ceiling slab of the first floor), to prevent rain water from flowing into the first floor.
Accordingly, the rain water flowing from the upper floors is stopped at the water stop floor, and does not flow into the first floor 72. The rain water stored on the floor slab 75 is discharged by a pump 76 to the outside of the building from an opening 79 for a window formed in a side wall 78 of the second floor 73 through a hose 77 (for example, see Patent Document 1: Japanese Patent Laid-Open No. 2004-84414).
The concrete multiple-story building such as a reactor building has a plurality of rooms on one floor. In the concrete multiple-story building described above, when an upper floor under construction is employed as the water stop floor, drainage water such as rain water is stored in the plurality of rooms, and a drainage pump needs to be installed in each of the rooms. Thus, it is difficult to effectively discharge the drainage water to the outside from the multiple-story building.
It takes as long as a few years to construct the concrete multiple-story building such as a reactor building, and during the construction period, sand or the like is mixed into the drainage water, and the sand mixed into the drainage water may clog the drainage pump, which may make it difficult to discharge the drainage water.